I. Field of the Invention
The present invention relates to a protective cover for a latch and lock cylinder to prevent removal of the lock cylinder or forcing of the door latch.
II. Description of the Prior Art
A typical door lock can be opened without a key in a number of ways by a knowledgeable person, for example, the cylinder of the lock can be removed to permit the lock mechanism to be operated directly; a sheet of flexible plastic can be inserted between the door jamb and bolt to force the bolt open; the door can be sprung, in the vicinity of the lock, in order to release the bolt; and the locking mechanism can be battered or removed. In order to combat this unauthorized entry, there are a number of protective devices available for locks and doors. One such device is disclosed in Mora, U.S. Pat. No. 2,114,075; wherein a rigid metal plate is bolted over a door lock having an opening therethrough for a key and a projection perpendicular to the door face adjacent the edge to engage a U-shaped projection on a second plate attached to the door jamb. This device protects aganist the removal of the cylinder and forcing the bolt with a plastic sheet. The disadvantage of this device are its relatively complex structure and difficulty of installation.
Another prior art disclosed in Jervis, U.S. Pat. No. 3,645,045 consists of two members: the first, a lock guard consists of a heavy plate with a recess to cover the end of the lock cylinder, and a raised edge to match the second member. An elongated hole opposite the lock cylinder is of such a size that a key can be inserted to operate the lock, but the lock cylinder cannot be removed. This plate is large enough to be bolted to the door over the lock regardless of the orientation of the lock. The second member consists of an elongated plate with a perpendicular projection. This second member is bolted to the door adjacent to the edge to protect the lock and the bolt. The disadvantages of this device are its relatively complex structure, its large size and installation difficulty.
No prior art device known to me provides the combination of attributes of the present invention, namely, a simple cylinder and lock guard providing a double layer of metal in the vicinity of the lock, smaller size, simple installation procedure, and attachment means to avoid the locking mechanism.